Performance of a Superior Bradyrhizobium japonicum and a Selected Sinorhizobium fredii Strain with Soybean Cultivars
Strain 532C of Bradyrhizobium japonicum has outperformed other soybean [Glycine max (L.) Merr.] rhizobia1 strains in Ontario trials conducted with cv. Evans. Strain HH303 of Sinorhizobium fredii has proven effective with some Ontario cultivars. The objective of this research was to compare the performance of 532C with that of USDA 110, CB 1809, a three-strain mixture, and HH303, by 16 commonly-grown, early-maturing soybean cultivars. Trials were conducted from 1988 to 1990 (only five cultivars were used in 1990) on soils that had low available N and had not grown soybeans previously. There were significant (P < 0.01) strain-by-genotype interactions for yield in all 3 yr and for seed protein content in 1988 and 1989, but interactions were small compared to main effects. Averaged over cultivars, strain 532C caused 11 to 17% higher seed yield than USDA 110 or CB 1809 in all 3 yr. Strain 532C appeared effective with all 16 cultivars tested. Strain 532C, used alone, caused higher average yields than the three strain mixture, which included 532C, only in 1988. The S. fredii strain HH303 caused consistently lower average yields than 532C, USDA 110, and the three-strain mixture, but average yields with HH303 and CB 1809 were not different in 1988 and 1989. Cultivars with cv. Evans in their pedigree yielded well with HH303. There were strong positive correlations (r = 0.75−0.85) between seed yield and seed protein contents. Strain 532C supported higher seed yields than the three-strain mixture at equivalent seed protein contents. Strain 532C was an effective N2 fixer with all cultivars tested and is now used in all soybean inoculants sold in Ontario.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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